So the basic way to think about playing the game is this: both players play their units (order matters), and use their soul skills to fight the opponent. Whoever wins is decided by whoever has the stronger bufs on field. The problem with Falkow, is that out of all 4 spheres, you have the worst start skill buffs, and if you get into straight fist fights with the opponent, you will generally always lose.
The one strength of Falkow, that which makes it different from other spheres, is your ability to change the state of the game to be in your favor through AGI manip (sylph and undine) and removals (return/tidal/cyclone). This being the case, in order to win with Falkow, it is essential that you use your returns in early/mid game to disrupt the opponent's field in able to win the match. In order to get to that point, you first need to have a few units on the field, AND have enough SP for your grims. This is why using a +2SS first can be so important, the extra SP will get you to that early game state where you have a few lvl 3 units on the field, with loose SP for returns. Secondly, the biggest mistake most beginner Falkow players make is that they iczer attack early. NEVER DO THIS. What happens when you iczer attack early is, you use 1SP for the iczer (so you are at -1SP compared to opponent), and then you usually trigger damage SS that kills your units, forcing you to spend SP reviving (more negative SP), and then since you're spending SP on revives and iczer, you won't be able to use returns, in which case you lose.
Sunbunman is one of the best WK players around though, so listen to him well!
The True Hero / Callonia